Iodine enriched kale (Brassica oleracea var. sabellica L.)—The influence of heat treatments on its iodine content, basic composition and antioxidative properties

Iodine deficiency in the diet globally continues to be a cause of many diseases and disabilities. Kale is a vegetable that has health-promoting potential because of many nutrients and bioactive compounds (ascorbic acid, carotenoids, glucosinolates and phenolic compounds). Brassica vegetables, including kale, have been strongly recommended as dietary adjuvants for improving health. The nutrient and health-promoting compounds in kale are significantly affected by thermal treatments. Changes in phytochemicals upon such activities may result from two contrary phenomena: breakdown of nutrients and bioactive compounds and a matrix softening effect, which increases the extractability of phytochemicals, which may be especially significant in the case of iodine-fortified kale. This study investigated changes of basic composition, iodine, vitamin C, total carotenoids and polyphenols contents as well as antioxidant activity caused by steaming, blanching and boiling processes in the levels of two cultivars of kale (green and red) non-biofortified and biofortified via the application to nutrient solutions in hydroponic of two iodoquinolines [8-hydroxy-7-iodo-5-quinolinesulfonic acid (8-OH-7-I-5QSA) and 5-chloro-7-iodo-8-quinoline (5-Cl-7-I-8-Q)] and KIO3. Thermal processes generally significantly reduced the content of the components in question and the antioxidant activity of kale, regardless of cultivar and enrichment. It was observed that the red cultivar of kale had a greater ability to accumulate and reduce iodine losses during the culinary processes. 8-hydroxy-7-iodo-5-quinolinesulfonic acid showed a protective effect against the treatments used, compared to other enrichments, thus contributing to the preservation of high iodine content.


4.
Figure S4.Percentage coverage of Recommended Daily Allowance for iodine (% RDA-I) and hazard quotient (HQ) for intake of iodine through consumption of 100 g and 50 g portions of leaves curly kale 'Oldenbor F1' and 'Redbor F1' before and after heat treatment in individual by adults 70 kg body weight; means followed by different letters for treatments, differ significantly at p < 0.05 (Duncan's post-hoc test); bars indicate standard error (n = 4).A. Daily Intake of I with 50 g of kale (µg I•day −1 ); B. Daily Intake of I with 100 g of kale (µg I•day −1 ); C. % RDA I (in 50 g portion of kale); D. % RDA I (in 100 g portion of kale); E. HQ for 50 g portion of kale; F. HQ for 100 g portion of kale.Homogeneous groups refer to a three-factor analysis of variance: factor No. 1 culinary treatment: raw, steaming, blanching, boiling x factor No. 2 type of enrichment: control, KIO3, 8-OH-7-I-5QSA, 5-Cl-7-I-8-Q x factor No. 3 kale cultivar: 'Oldenbor F1' and 'Redbor F1'.

Figure S4 .
Figure S4.Percentage coverage of Recommended Daily Allowance for iodine (% RDA-I) and hazard quotient (HQ) for intake of iodine through consumption of 100 g and 50 g portions of leaves curly kale 'Oldenbor F1' and 'Redbor F1' before and after heat treatment in individual by adults 70 kg body weight; means followed by different letters for treatments, differ significantly at p < 0.05 (Duncan's post-hoc test); bars indicate standard error (n = 4).A. Daily Intake of I with 50 g of kale (µg I•day −1 ); B. Daily Intake of I with 100 g of kale (µg I•day −1 ); C. % RDA I (in 50 g portion of kale); D. % RDA I (in 100 g portion of kale); E. HQ for 50 g portion of kale; F. HQ for 100 g portion of kale.Homogeneous groups refer to a three-factor analysis of variance: factor No. 1 culinary treatment: raw, steaming, blanching, boiling x factor No. 2 type of enrichment: control, KIO3, 8-OH-7-I-5QSA, 5-Cl-7-I-8-Q x factor No. 3 kale cultivar: 'Oldenbor F1' and 'Redbor F1'.
'; means followed by the same letter are not significantly different p < 0.05 (Duncan's post-hoc test).

Table 2 .
Iodine content (mg•L -1 ) of the water after boiling the of curly kale leaves of both cultivars 'Oldenbor F1' and 'Redbor F1' with or without biofortification.

Table 3 .
Chemical composition of kale 'Oldenbor F1' and 'Redbor F1' in fresh tissue before and after heat treatment.

Table 4 .
The antioxidant activity and content of total phenolics, total carotenoids, and ascorbic acid in kale 'Oldenbor F1' and 'Redbor F1' before and after heat treatments.